1. Field of the Invention
This invention relates to connecting of telephone calls and, more particularly, to connecting of telephone calls over internet protocol networks.
2. Background Information
The traditional telephone network is a switched network that provides users with a dedicated end-to-end circuit for the duration of each call. Circuits are reserved between the originating switch, tandem switches (if any), and the terminating switch based on the called party number to create the end-to-end circuit.
Recently, telephone calls have been transmitted over digital networks using packet switched internet protocol (IP) networks, termed voice over IP (VoIP) transmission. Packet-switched IP networks provide shared, virtual circuit connections between users. Voice information to be transmitted across an IP network is converted into digital data and broken up into multiple, discrete packets. Individual packets may travel over different network paths to reach the final destination where the packets are reassembled in the proper sequence to reconstruct the original voice information. The transmission speed between any two users can change dramatically based on the dynamic number of users sharing the common transmission medium, their bandwidth requirements, the capacity of the transmission medium, and the efficiency of the network routing and design.
VoIP transmission typically costs less than transmission over traditional public switched telephone networks (PSTNs). A disadvantage of VoIP networks is the variability of the quality of the signal received at the destination as determined by changing network conditions. The received signal quality depends on a large number of variable network factors such as packet loss, packet latency, queuing delay, and bandwidth availability. These network factors will vary depending on the volume of network traffic and the location of the destination. The IP network, unlike the traditional public switched network, is not uniformly or predictably suitable for voice quality transmission.
Prior art systems for connecting calls over IP networks have monitored the quality of service (QoS) provided by the network and disabled the gateway to the IP network when QoS fell below an acceptable level. However, QoS is not a uniform characteristic in an IP network. QoS is dependent on the destination and it may be unacceptable for transmissions to one destination but be acceptable to another destination. Accordingly, what is needed is a method and apparatus for monitoring the quality of service (QoS) of the IP network and connecting a telephone call over an alternate network, on a call by call basis, if the QoS of the IP network is unacceptable based on the destination for the call.
An apparatus causes alternate connection of a telephone call directed to an IP network if the quality of service provided by the IP network is less than a predetermined threshold. A network monitor measures a transmission rating factor for the IP network. An IP network interface, coupled to the network monitor, an originating system, and the IP network, receives the telephone call for a dialed number from the originating system. The IP network interface causes the originating system to connect the telephone call through a first network if the measured transmission rating factor for the IP network is less than the desired transmission rating factor, and connects the telephone call through the IP network otherwise.